>> We'd like to say that we're aware itch.io locks users out of the expansion pack download on the store page. We have to manually send each user a separate download key for the expansion pack and will do so once the standalone expansion pack page is ready and the team has had a bit of time to breathe.
Steam key: https://itch.io/t/67604/how-to-get-a-steam-key-from-your-itchio-purchase